The present disclosure relates to solid-state image sensors and electronic apparatuses, and particularly relates to a solid-state image sensor and an electronic apparatus which are capable of obtaining high-quality images.
In a general solid-state image sensor, pixels receive light transmitted through three-primary color filters, for example, in a light receiving plane in which the pixels having photoelectric conversion elements which convert light into charges are arranged in a planar manner. For example, in a general solid-state image sensor employing color filters of Bayer arrangement, a pixel unit including four pixels, i.e., one red pixel, two green pixels, and one blue pixel, which are combined with one another is used.
Furthermore, in recent years, a pixel unit including other colors in addition to the three primary colors has been proposed. For example, a pixel unit including four pixels, i.e., a red pixel, a green pixel, a blue pixel, and a white pixel, which are combined with one another has been proposed. The white pixel which does not have a color filter is added in this pixel unit. In this way, when the number of colors of the color filters used in the solid-state image sensor is increased, color reproducibility is improved.
Referring now to FIG. 1, a solid-state image sensor employing color filters of six colors, i.e., red, green, blue, cyan, magenta, and yellow will be described, for example. FIG. 1A is a diagram schematically illustrating a configuration of a light receiving plane of a solid-state image sensor. FIG. 1B is a diagram illustrating CIExy chromaticity which is a color system defined by the CIE (Commission Internationale de l'Eclairage).
As illustrated in FIG. 1A, a solid-state image sensor 11 includes a plurality of pixels 12 arranged in a matrix and vertical transmission paths 13 which transmit pixel signals output from the pixels 12 and which are arranged between columns of the pixels 12.
The solid-state image sensor 11 further includes pixel units 14 each of which is configured by combining a pixel 12-1 which receives red (R) light, a pixel 12-2 which receives green (G) light, a pixel 12-3 which receives blue (B) light, a pixel 12-4 which receives cyan (C) light, a pixel 12-5 which receives magenta (M) light, and a pixel 12-6 which receives yellow (Y) light with one another. Then the pixel units 14 which receive six color light beams are periodically arranged on the entire light receiving plane of the solid-state image sensor 11.
Although the solid-state image sensor 11 capable of receiving multi-color light has high color reproducibility, resolution is degraded. Specifically, in the solid-state image sensor 11, pixels which receive the same color light are spaced away from each other by a pitch corresponding to three pixels in a row direction and a pitch corresponding to two pixels in a column direction.
FIG. 1B represents that a color region represented by six colors (a hexagonal region defined by vertices denoted by triangles in FIG. 1B) has higher reproducibility than a color region represented by three primary colors (a triangle region defined by vertices denoted by circles in FIG. 1B).
However, a solid-state image sensor capable of performing color processing of multiple colors including four colors or more has high color reproducibility but has low resolution. Furthermore, color detection of retinas of human beings is based on three primary colors, and therefore, even when the number of colors is increased, considerably large effect is not expected. On the other hand, since the resolution is degraded when the number of colors is increased, a method for preventing the resolution from being degraded even when the number of colors is increased is demanded.
Note that a display apparatus which is provided with color filters for four colors i.e., red, green, blue, and yellow, to improve color reproducibility has been developed. Furthermore, in the future, development of a display apparatus for professional use which is provided with color filters of four colors or more to further improve the color reproducibility is expected. However, colors which are subjected to signal processing performed by an image pickup device are three colors including red, blue, and green (or four colors additionally including white).
Here, Japanese Unexamined Patent Application Publication No. 2006-270364 discloses a solid-state image sensor including small complementary color pixels embedded in gaps among pixels of red, green, and blue. However, since each of the complementary color pixels includes a dual-wavelength signal in this solid-state image sensor, charges generated by the complementary color pixels reach nearly twice as much as those generated by the red, green, and blue pixels. Accordingly, it is considered that amounts of charges are saturated in the small complementary color pixels and false color is generated.
Furthermore, Japanese Unexamined Patent Application Publication No. 2006-165567 discloses a solid-state image sensor in which a plane coverage of pixels is improved by covering a plane by hexagonal pixels.
Moreover, Japanese Unexamined Patent Application Publication No. 2010-161200 discloses a solid-state image sensor in which a periodic structure is configured by a unit of seven hexagonal pixels. However, this solid-state image sensor has a complicated periodic structure, and therefore, signal processing performed for outputting pixel signals is also complicated.